At present, to prevent the above phenomenon of surface conductivity of the insulators, maintenance operations are carried out, consisting in a more or less frequent washing of said insulators. This operation is carried out by deenergizing the line and manually washing the insulator. Nevertheless, these out-of-commission intervals on the line create problems for the users, so that it would be desirable to reduce them to a minimum.
For this purpose, the washing operation is also carried out on the live line, by spraying jets of detergent fluid from a distance sufficient to prevent discharges between the live parts and the spray nozzle, but with evident risks for the operators. Besides, this system is on one hand apt to determine discharges on the insulator--especially on mean-voltage lines, wherein the insulator is fairly small and is thus thoroughly hit by the fluid jet--and on the other hand it is scarcely efficient, due to the great distance between the nozzle and the insulator.
An improved apparatus, in respect of the simple washing jet controlled by a ground operator, is that described in the DE-A-2123203, which comprises a tubular U-shaped member provided with a plurality of nozzles, to which detergent fluid is fed through a pipe connected to a reservoir placed on the ground. The tubular U-shaped member is fixed to the end of an insulating rod, which is handled by an operator standing onto the bracket of a pole supporting the insulator to be washed. The operator moves the insulating rod so as to keep the tubular U-shaped member substantially centered in respect of the insulator, so that the jets of detergent fluid sprayed from the nozzles may reach the entire surface of the insulator. The operator must also move the insulating rod so as to shift the tubular U-shaped member along the whole insulator.
Nevertheless, this apparatus has at least the following drawbacks:
the operator has to work in difficult conditions, as he is expected to climb up onto the pole bracket and to operate with a very long rod (the rod is certainly longer than 4 or 5 m, as it has to reach every part of the insulator), which is therefore awkward to handle; PA1 these difficult operating conditions are in contrast with the fact that the operation must be carried out with high precision, keeping the tubular U-shaped member always centered in respect of the insulator and shifting said tubular U-shaped member along the whole length of the insulator; PA1 the whole washing operation is very slow, since the single tubular U-shaped member has to be shifted along the entire insulator, making sure that the washing is carried out properly on each part thereof; to this there should be added the fair amount of time required for the operator to reach his working position; PA1 the insulating conditions are quite precarious, since the tubular U-shaped member--merely operated by means of the long control rod--can easily get in contact with the body of the insulator and, in certain circumstances, favor an electric discharge along the actual insulator.
The DE-A-3310764 adds nothing to the teaching of the DE-A-2123203, except for suggesting to use a special detergent fluid, apt to facilitate removal of the dirt collected onto the insulator.
The AT-B-335548 concerns instead a washing apparatus comprising a two-valve boxlike body which totally envelops the insulator and into which is circulated the detergent fluid. Since the boxlike body encloses the electric conductor as well as the support base of the insulator, this apparatus can practically be used only after the line has been deenergized. In the contrary event, there would be serious problems of insulation and great risks of electric discharges between the pole bracket and the conductor.
The main object of the present invention is a process and an apparatus for washing insulators, of the type described in the introductory part of claims 1 and 14, by means of which it is possible to carry out the whole washing operation rapidly, while avoiding or reducing to a minimum the risk of electric discharges along the insulator. Another object of the invention is to propose an apparatus which is particularly suited to be fully automated. All these results are obtained thanks to the characteristics described in the characterizing part of claims 1 and 14.
In actual fact, by providing to anchor and center the washing head on the insulator and by using a plurality of tubular U-shaped members, each having a plurality of spray nozzles, it is possible--on one hand--to greatly facilitate the correct, automatic positioning of the washing head, centering the nozzles in respect of the insulator, and--on the other hand--to very rapidly carry out the washing, for example by simply changing over the feeding of detergent fluid from one tubular member to another, and all this in safe conditions, thanks to the fact that the tubular members are electrically insulated one from the other.
According to a particular embodiment, the washing of the insulator is carried out in parts, at different levels, by hitting in succession single parts of the insulator with said jets of detergent fluid, while simultaneously blowing drying air on the other parts.
By the term "single parts of the insulator" is meant both a single petticoat and two or more petticoats of the insulator, that is, in any case, only a single portion of the entire insulator system--whether it be a pin insulator or an insulator chain--interposed between the earth and the live line.
Different considerations lie at the basis of the invention: on one hand that, the more powerful, abundant and uniform the wash, the less the risk of discharges along the insulator surface; on the other hand that, a powerful and uniform wash also improves the quality of the cleaning operation; furthermore that, it is practically impossible to carry out a sufficiently powerful wash with jets sprayed from nozzles, which are so far as to guarantee a kind of insulation simply on account of the distance; and finally that, a safe insulation towards the operator can more easily be obtained with a suitably insulated support, even if it is quite close to the insulator.
Moreover, the possibility offered by the invention to operate close to the surfaces being washed, allows to use positively lower quantities of detergent fluid, which reduces both the problems of supply and those of local pollution, in case of having to use a polluting detergent.
According to another important aspect of the invention, it has been proved that, even in hard conditions, with higher voltages, any risk of discharges can be avoided if the insulator is washed in parts, at different levels, that is, if the washing is carried out on one part of the insulator at a time, while the other overhanging or underlying parts are forcedly kept dry.